This project focuses on illness behavior and somatization in children and adolescents, i.e., the development of symptomatology and disability disproportionate to the medical condition. The research is conceptualized within the context of family health and illness behavior. Learning to recognize and respond appropriately to bodily sensations is viewed as a normal process in child development and somatization is viewed as an extreme on a continuum of normal behavior. The research is grounded in a conceptual model that identifies child and family factors associated with the development and maintenance of excessive somatic complaints and disability. The first specific aim is to test the model using a patient population in the context of a longitudinal design that traces over time the level and nature of symptomatology/disability in pediatric patients with recurrent abdominal pain of no identifiable organic etiology. Several comparison groups will be used in order to test the specificity of the model, i.e., its utility in distinguishing children with functional somatic complaints from well children and from those with identifiable organic disease or emotional disorders. Developmental differences in the specific components and overall utility of the model also will be examined. The second specific aim is to examine, via three experimental studies, the processes linking the model components. These studies will test the following major hypotheses: (a) a child's symptom-reporting will increase and physical performance will decrease under conditions that encourage the child to monitor internal bodily sensations, (b) parents' perceptions of their own bodily states will influence their interpretation of children's bodily cues as being indicative of illness, and (c) under conditions of physiological arousal children will report physical symptoms and fatigue to a parent who has previously reinforced their illness behavior.